Rod shock absorber



Dec. 29, 1970 w. N. SUTLIFF Er'AL 3,551,012

ROD SHOCK. ABSORBER Filed Dec. 23, 1968 //v VE/V 70/?5. 25 WAY/V5 /v. SUTL/FF ,7 JIM L. DOW/VE/V l3 g 4 r ram/v5 Y.

United States Patent 3,551,012 ROD SHOCK ABSORBER Wayne N. Sutliif and Jim L. Downen, both of 2931 Pierce Road, Bakersfield, Calif. 93308 Filed Dec. 23, 1968, Ser. No. 785,977 Int. Cl. F16b 7/00 U.S. Cl. 287-103 2 Claims ABSTRACT OF THE DISCLOSURE An elastic flexible cable forming a tension link inserted between an adjacent pair of deep well pump sucker rods, said link being enclosed in a tube which, in case the cable breaks, confines the cable strands, preventing their bushing, said tube also providing a safety over-riding tension link which thereupon assumes the function of a solid link connecting said adjacent sucker rods.

BACKGROUND OF THE INVENTION The deeper that wells are drilled, the greater the tendency is for the well bore to wander from vertical. Sucker rod strings are subject to high and complex strains when operating in such wells which results in frequent breaking of the string due to metal crystallization.

Many efforts have been made to alleviate this problem but without complete success. It is within this field of endeavor that the present invention offers a new solution to an old problem.

SUMMARY OF THE INVENTION The theory on which the present invention operates is that sucker rod failure in deep oil wells often results from a solid steel rod member being simultaneously subjected to a complex of stresses, which, focusing repeatedly in a small area of the rod, break down the crystal structure of the metal and thus promote an early rod failure.

It is an object of the present invention to provide a means of distributing heavy strains more uniformly over the entire sucker rod string and particularly to prevent such strains becoming excessive due to sudden changes in direction at the top and bottom of each reciprocation.

Another object is to minimize in certain local areas the development of heavy repetitive tension or compression strains in conjunction with heavy bending strains.

A further object is to introduce into a conventional sucker rod string,,the rods of which are made of solid steel, a link of equivalent tensile strength but having a higher capability of flexing without suffering damage to itself whereby said sucker rod string is enabled to fit around an angular change in the direction of a well bore without producing excessive strains in the structure of the sucker rod string.

A further object is to utilize for such a link, a heavy twisted steel wire cable in such a manner that this will add flexibility to the sucker rod string in an area where this link is allowed to function, and in addition, provide a substantial degree of resilience or capacity for elongation under tension, thereby absorbing sudden shocks ordinarily imposed on a very long string of rods.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a preferred embodiment of the rod shock absorber of the invention.

FIG. 2 is an enlarged fragmentary longitudinal sectional view taken on the line 22 of FIG. 1, and illustrates the invention in its normal operational condition.

FIG. 3 is a sectional view similar to FIG. 2 and illustrates the invention as it functions to hold adjacent sucker rods of a sucker rod string together following the breaking of the cable of the invention.

3,551,012 Patented Dec. 29, 1970 DESCRIPTION OF THE PREFERRED EMBODIMENT The rod shock absorber of the invention comprises a relatively flexible, elastic link 10 in a sucker rod string 11 which makes screw connections respectively at its upper and lower ends with sucker rods 12 and 13 of said string. The link 10 of the invention includes upper and lower subs 14 and 15. These subs have respectively upper and lower pin boxes 16 and 17 into which threaded pins 18 and 19 of upper and lower sucker rods 12 and 13 respectively are screwed.

Formed concentrically with the upper pin box 16 of upper sub 14 and extending downwardly therefrom is a tubular cable mounting sleeve 20 from the lower end of which a relatively thin walled tubular apron 21 extends downwardly.

Formed concentrically with the lower pin box 17 of lower sub 15 is a tubular cable mounting sleeve 25. A section 26 of heavy twisted steel Wire cable (having heads 27 and 28 formed at its upper and lower ends) is provided with a housing tube 29 which encloses a substantial lower portion of the cable between the heads 27 and 28. A heavy annular shoulder 30 extends outwardly from the upper end of tube 29, and prior to the assembly of the device, a heavy steel washer 31 is shifted upwardly over the tube 29. The lower end of cable 26 and the lower head 28 thereof and a lower end portion of tube 29 are now inserted downwardly in the cable mounting sleeve 25 of lower sub 15 and said cable and tube are permanently united with sleeve 25 by swedging the latter inwardly thereagainst.

With the tube 29 and cable 26 thus secured rigidly to lower sub 15, a substantial upward portion of the cable 26 extends upwardly above the upper end of tube 29. Said upper end portion of the cable and the upper end portion of the tube 29 are thus inserted upwardly into the apron 21 and the exposed portion of the cable is inserted into the tubular cable mounting sleeve 20 of the upper sub 14 and said sleeve is swedged inwardly against the upper portion of said cable to permanently unite the two together.

The heavy steel washer 31 is now shifted upwardly along the tube 29 into contact with the lower edge of the cylindrical apron 21 on upper sub 14, and welded thereto, thus rigidly uniting this washer with said apron.

The fabrication of link 10 comprising the rod shock absorber of the present invention, having been completed as above described, and the pins 18 and 19 of sucker rods 12 and 13 having been screwed into the internally threaded boxes 16 and 17 of the upper and lower subs of said link, the sucker rod string 11 now functions in the following manner:

OPERATION With the shock absorber operating in its normal condition as shown in FIG. 2, tensional strains imposed on the link 10 of the invention are assumed entirely by the cable 26. compressional strains imposed on said link are assumed entirely by cable housing tube 29. There is a certain amount of linear resiliency displayed by a twisted cable such as the wire cable 26 when subjected to extremely high tensional strains and the presence of this cable in link 10 with the latter embodied in the sucker rod string 11 modifies any linear tensional shock which the string 11 is subjected to ordinarily by the whipping action with which a walking beam supporting the sucker rod string at the upper end of the well halts its downward movement and starts to lift the entire string upwardly on the return stroke, during which said rod must lift with it the entire weight of the column of pumped liquid then supported by the plunger of the pump which is suspended on the lower end of the string 11. The degree of resiliency thus imparted-to the string 11 by the resilient cable link introduced into the string by the present invention relieves the sucker rod string from the full severity of the strains normally otherwise imposed thereon by the rapid succession of whipping changes in direction which are normally inherent in the operation of a deep well pump through a string of sucker rods.

The rod shock absorber also relieves sucker rod string 11 from abnormal strains produced by the solid metal of the sucker rods being subjected to substantial bending moments coincidentally with the whipping action of alternate tensional and compressional forces applied in rapid succession in the reciprocation of the sucker rod string in performing its pumping function. This relief of the sucker rod is effected by the capacity of the link 10 of the invention to bend within the degree of liberty which the tube 29 has by its freedom to flex within the opening 32 of the washer 31 and by the relatively loose relationship between the cable 26 and the tube 29 housing the same. Whether this slight bending action afforded by the rod shock absorber at the location there of the apron 21, takes place during a subjection of the sucker rod string to maximum tensional strains, as on the upstroke, or during maximum compressional strains, as on the downstroke, the flexibility of the cable 26 permits this flexing of the link 10 to take place without any damage being done to the structure of the link.

The invention embodies within it means for utilizing a cable as a flexible link between adjacent sucker rods in a sucker rod string for the protection of the sucker rods from crystallization and does this in such a manner that no danger is encountered due to the bushing of the strands of the cable in case, due to long Wear or abnormal strains, the cable should break. This object is accomplished in the present invention by completely confining the cable of the link so that if it does break, the broken strands of the cable will be entirely confined by the cable housing tube 29 and the apron .21.

The invention further provides that, should the cable thus break, the sucker rods 12 and 13 of the string 11 to which upper and lower ends respectively of the link 10 are connected will continue to be connected by the annular external shoulder 30 provided on the upper end of tube 29 coming into contact with the steel Washer 31 of the apron 21 as shown in FIG. 3. This provides a flexible joint in the link 10 through which the pump may continue to be reciprocated through the sucker rod string 11 after the cable breaks and it will in any event permit the recovery of the portion of the sucker rod string 11 located below the link 10 after the cable of the link has broken.

While only one preferred embodiment of the present invention has been disclosed in the present application, it is to be understood that this disclosure is for illustrative purposes only and that the invention is not to be con sidered as limited to the specific details of this disclosure but is subject to various modifications and changes all within the spirit of the invention and in the scope of the appended claims.

We claim:

1. In a shock absorber for a string of sucker rods, the combination of:

upper and lower subs adapted to be connected respectively with an adjacent pair of sucker rods in said string;

a section of heavy twisted wire cable;

means for rigidly uniting upper and lower end portions of said cable respectively to said upper and lower subs, said lower sub and the rods therebelow being thereby suspended by said cable from said upper sub;

a cable housing tube surrounding said cable between said subs to act as a compression member for transmitting compressive forces from one of said subs to the other sub;

said lower sub having a central recess receiving lower end portions of said tube and cable which are retained concentrically therein by swedging; and

lost motion means flexibly connecting an upper end portion of said tube to said upper sub, including a cylindrical apron extending downwardly from said upper sub to enclose said upper portion;

an annular external shoulder on said upper portion; and

an annular internal shoulder provided on the lower end of said apron and underlying said external shoulder on said tube;

said shoulders providing support for said tube only in the event of said cable breaking.

2. A flexible shock absorber for interposition in a string of sucker rods, comprising:

an upper sub;

a lower sub;

a cable united at its ends to said subs;

a tube housing said cable and rigidly united at one end to said lower sub,

the other end of said tube being spaced axially a short distance from end-to-end contact with the upper sub when said cable is taut;

an apron provided on said upper sub and extending downwardly over but radially spaced from and loosely enclosing the upper portion of said tube;

an external annular shoulder on the said other end of said tube and radially spaced from said apron; and

an internal annular shoulder extending inwardly from said apron and radially spaced from said tube, said shoulders overlapping radially but being spaced axially from each other and allowing said tube freedom to swing through a substantial angle out of alignment with said upper sub to accommodate flexing of said string of rods;

said shoulders interengaging upon said cable breaking,

to maintain a connection between said subs.

References Cited UNITED STATES PATENTS 969,755 9/1910 Spang 175305 1,016,106 1/1912 Soderstrom 175-321 1,144,814 6/l9l5 Cleveland 175-305 1,544,041 6/1925 Schirnhofer 175299 3,015,512 1/1962 Oakes 287X 3,303,894 2/1967 Varney 321X 1,030,387 6/1912 Critton 287104X 1,779,793 10/1930 Yungling 285117 1,845,061 2/1932 Schmalz 285-117X 1,982,915 12/1934 Jenks 287-Frangible 2,839,315 6/1958 Arterbury et al 2853 DAVID J. WILLIAMOWSKY, Primary Examiner A. V. KUNDRAT, Assistant Examiner s. c1. xn, 285-117 

